The 2025 quarterly deadlines (don't miss these)
Q1 2025 — due April 15, 2025. Covers income earned January 1 through March 31.
Q2 2025 — due June 16, 2025 (the 15th is a Sunday). Covers April 1 through May 31 — yes, only two months, the IRS math is weird.
Q3 2025 — due September 15, 2025. Covers June 1 through August 31.
Q4 2025 — due January 15, 2026. Covers September 1 through December 31.
Miss a deadline and the IRS assesses an underpayment penalty — currently about 8% APR, compounded daily, applied per quarter. For someone owing $12,000 and paying three months late, the penalty runs roughly $240.
Example: $90,000 freelancer with no W-2 wages
Net Schedule C income: $90,000. SE tax: $90,000 × 0.9235 × 15.3% = $12,716. Half is deductible from AGI — $6,358. Taxable income (single, standard deduction): $90,000 − $14,600 − $6,358 = $69,042. Federal income tax at 2025 single brackets: about $10,095. QBI deduction (20% of $69,042): ~$13,808, bringing taxable to $55,234 and tax to about $6,861.
Total 2025 federal liability: ~$19,577 (SE + income − QBI). Quarterly payment: $4,895. Add state tax — a California freelancer with the same income owes roughly another $4,200 annually, or $1,050/quarter.
The safe harbor rule — the cheat code
The IRS will not assess a penalty if your total withholding + estimated payments for the year meet either:
(1) 90% of current-year tax liability, or
(2) 100% of last year's tax liability (110% if your prior-year AGI was over $150,000).
The second rule is the easier one to hit. If you owed $18,000 in federal tax last year, pay $4,500 per quarter this year and you're safe no matter how much more (or less) you actually owe when you file. Any shortfall gets paid in April without penalty. This is huge for anyone whose income swings year to year.
W-2 + 1099 mixed income: withhold extra instead
If you have both a W-2 job and side-hustle 1099 income, the cleanest move is to skip quarterly vouchers entirely and instead bump up your W-2 withholding to cover the extra tax. Withholding counts as paid evenly across the year regardless of when it actually came out of your paycheck, which kills the quarterly-deadline penalty math.
Use Form W-4 Step 4(c) "Extra withholding" — divide your expected 1099 tax by remaining pay periods and enter that dollar amount. Check in October to see if you need to adjust.
How to actually pay
Three options, all equal in the IRS's eyes:
IRS Direct Pay (irs.gov/payments) — free, ACH from your bank account, takes 30 seconds once you've done it. Save the confirmation number.
EFTPS (eftps.gov) — better for business owners, allows scheduling a year of payments in advance. Enrollment takes 5–7 business days via mailed PIN.
Mail Form 1040-ES with a check — slowest, most error-prone. Only use it if the other two aren't options.
Do not pay by credit card unless you're farming points — the processor fee (1.75–1.85%) eats any tax benefit.
Annualized income installment method (for lumpy income)
If your income is seasonal — a contractor with a big Q3, a course creator with a launch in Q4, a consultant with a single large invoice in December — you can pay estimates based on what you actually earned each quarter, not an even split. File Form 2210 with your return to reconcile.
This matters because the standard penalty calculation assumes equal quarterly earnings. A $200K consulting project billed in November does not require a $50K payment in April. Use Schedule AI on Form 2210 to prove the income came in Q4 and you only owed the related tax in Q4.
State estimated taxes — usually the same schedule
Most states follow the federal quarterly schedule with the same due dates. California requires a different breakdown: 30% of total in Q1, 40% in Q2, 0% in Q3, 30% in Q4 — front-loaded to speed up state cash flow. New Jersey uses the federal schedule but at different rates. Check your state's 1040-ES equivalent form for the specific rules.